Gadget Freak Case #247: Back to the Manual Mill

Our teenage gadget master John Duffy has created a manual mill you can make in your home shop.

Electronics have sidelined the manual mill in recent decades, but Duffy has created a manual mill that incorporates modern parts, such as an Arduino. He considers it a cheap replacement for a much more expensive machine. He goes through great detail in the instructions to create this mill. The mill has up to 1/1000th accuracy on X and Y and about 1/100th on Z.

I like your approach to developing PoCs (Proof of Concepts) by researching what already exists and doing a remix to solve a specific problem. Re-purposing what's available in one's junk box or lab is definitely a good method of reducing development cost and expediting the PoC build. I enjoy your Gadget Freak videos and look forward to seeing more of them in near future. Keep the vision alive and clear as well as the Product Development projects.

Thanks, and I usually get ideas either from seeing something someone else did. For my first gadget freak, the wireless lanterns, I got the idea from MAKE magazine, when I saw the project, I thought that the lanterns were glued shut, so I thought of how they might be recharged without opening them. The other two were for the object that I actually made, not just as a proof of concept. The really big lantern was made because I go to a summer camp for Boy Scouts, and we have to use tiny flashlights or propane lanterns for light. This one was because I use mills at robotics, and thought it would be really useful to have one at home for personal projects. If you mean the method by which I make them, it is all just looking online and through the few issues of popular science and MAKE that I have, for designs and components for similar functions (the joule theif from a MAKE video for the lanterns, a CPU cooler for the other light). For this, I looked up many methods of determining distance for the DRO before settling on encoders, and many displays before settling on the TV, and even several different microcontrollers before going with the arduino (my first thought was a teensy, as they are cheaper and smaller, but I had an extra arduino already).

Great video and project. I'll be showing this video to my electronic students to inspire and motivate them to build their projects for submission to the Design News Gadget Freak column. Just curious, where do you get inspiration for your projects?

I am aware of, and I do keep backlash compensation in mind. I am not really concerned about wear, as I don't plan on using this specific one for a long time, I do plan to upgrade to a "real" mill soon.

As for diminishing returns, that's actually how I generally gauge how interrested I *really* am in a project, if I finish a revision, then don't spontaneously start redesigning and rebuilding bits of it, I'm generally not very interrested. Many projects, however, which I do improve are generally just as rewarding to improve as to make in the first place.

Your mill looks pretty good to me. A project like this offers many lessons. As you use it I am sure you will find new and interesting issues.

Don't jump to fault it too quickly. All mills have accuracy issues if not used with care and within their capabilities.

The lead error of your drill rod is more than likely pretty good. The greater issue may be wear. This is the main reason to use an Acme thread rather than a higher angle machine thread. A ball screw is even better but still has many similar limits.

As for backlash, you don't actually need to worry about this too much as long as you approach your tool position from the same direction all of the time. It's quite common to simply add moves to take up the backlash when necessary. Even with a good ball screw it can be a good practice.

Rigidity mainly effects how heavy of a cut you can take. For accuracy you can always take a number of lighter cuts as you reach your final position. This is true even with a very rigid machine. Remember that the part and tool holder deflect too. Much of the time this is the real limit.

Modern machine tools are actually much less rigid than their predecessors of many years ago. It was found better to simply take a greater number of lighter cuts rather than build the ultimate in rigidity. Sort of a speed vs. brawn thing. Well $$ had a lot to do with it too.

Sure your mill can be improved a lot but always remember the reality of diminishing returns.

For more stiffness, check out the "SuperStrut" at Home Depot. They carry a limited range of stuff to bolt it together.McMaster-Carr has a wide range of accessories. Search there for Strut Channel. Take a look and then go to your local Electrical Supply Wholesaler.

To see it in action, look up at any big box store. It will be supporting conduit, refrigeration lines, and almost anything else they hang from the rafters.The sturt isn't cheap, but it may be the least expensive way to get the stiffness you need. Because of the accessories, it may be easier to put together than chunks of aluminum. You could save on accessories by welding joints.

For the other old guys out there, using the strut is like a big-boy Erector Set.

John--let me first congratulate you on your creativity then indicate I agree completely with your comments about the level of understanding relative to STEM subjects. I run across individuals who seem to delight in telling everyone that engineering, manufacturing and particularly R&D work is for those who can't do anything else. I have one lawyer "friend" who can't do much more than turn on a light switch yet he wants to save the world. Your mill is an excellent example of creative engineering at its best. Please keep up the passion for "invention"--it got us to the moon, and back.

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